Won't Shutdown...restarts instead.

[Guest]

I have a Toshiba satellite A135-S4427 Laptop with Vista Home premium
preinstalled on it. I have had it for a couple of months and recently have
had problems when I use the shutdown button in start menu or in the task
manager window or anything that gives me shutdown options. I click on
shutdown and the computer logs off, then starts shutdown process ( which
takes a few seconds to 30 seconds), and then shuts off. But, it is off for
about a second or two and it restarts. I have tried checking to make sure the
buttons are set for shutoff and they are. I have scanned computer for malware
in safe mode and found only cookies. I have looked at the logs for
performance issues and have found a few .exe apps that have not shut down
right but I never have the same thing happen in any of the shutdown logs.
Most times it shows no error. There is obviously something causing it to
restart after shutdown but I have no clue as to what. Any ideas anyone that
might fix this problem as it takes holding the power button down to manually
shut it down and stay off???

 

[Guest]

I noticed with some experimentation that this problem only occurs when the
A/C is plugged in. When shutting down on battery power it shuts down fine.